High current electrical joint apparatus

ABSTRACT

Electrical joint apparatus includes an array of stab connectors each having plural contact fingers and an array of receiver connectors each having contact fingers arranged in lapped relation with the contact fingers of an associated stab connector. A clamping rod extends freely through apertures in the stab fingers and carries springs at each end of the stab connector array. A first cam follower, affixed to one end of the rod, and a second cam follower movably supported on the rod, are driven in opposite directions by a cam, such as to uniformly load the springs and thereby develop equal and oppositely directed forced clamping the lapped fingers in electrical interconnection.

BACKGROUND OF THE INVENTION

Drawout apparatus are well known expedients for facilitating theinstallation and removal of physically large electrical devices, such asswitches and circuit breakers, with respect to switchboards andpanelboards. The device is provided with plug-in or stab-type disconnectprimary contacts which mate in electrical interconnection withcomplementary switchboard primary disconnect contacts incident toracking movement of the device to its innermost, engaged position,thereby making the electrical joints requisite to electricallyconnecting the device into the switchboard.

In higher current applications, the devices become quite large andheavy, thus rendering the bodily movement of the devices necessary toelectrically connect and disconnect them from the switchboard extremelycumbersome without structure supporting the device in its rackingmovement. Moreover, as current ratings increase, the requisite highcontact pressures embodied in the primary disconnect contacts becomeextremely difficult, if not impossible, to overcome without mechanicalassistance. Thus, drawout apparatus for accommodating these largerelectrical devices typically include not only provisions for supportingthe device during racking movement, but also various camming or leveringmechanisms operating to mechanically assist the racking movement of thedevice at least during that segment of travel necessary to engage anddisengage the device-switchboard primary disconnect contacts.

The principle limitation to the utilization of drawout apparatus is theability of the plug-in primary terminal joints to carry the increasinglyhigher currents called for in many applications. These joints aresources of heat which can contribute to an intolerable high temperaturecondition within the switchboard. The spring forces incorporated in suchplug-in terminal connectors and their mutual contact surface areas,which will accommodate sliding relative movements of the matingconnectors incident to making and breaking the plug-in joints, are notsufficient to achieve a cool running joint in high current applications.Consequently, bolted terminal joints must be resorted to, and, as aresult, the signal advantage in drawout installations of being able toconnect and disconnect a device from a live switchboard without havingto operate directly on the primary terminal joint is lost.

It is accordingly an object of the present invention to provide improvedelectrical joint apparatus of high current capacity having particularbut not limited application in switchboard drawout apparatus.

An additional object of the present invention is to provide electricaljoint apparatus of the above character, which is operable tosimultaneously make plural electrical joints from a removed, safelocation.

A further object of the present invention is to provide joint apparatusof the above character, which is operable to make plural reliableelectrical joints in highly repeatable fashion.

Yet another object of the present invention is to provide jointapparatus of the above character capable of perfecting electrical jointshaving all the characteristics and attributes of bolted joints.

An additional object is to provide electrical joint apparatus of theabove character which is efficient in design and conveniently manuallyoperable in a rapid fashion.

Other objects of the invention will in part be obvious and in partappear hereinafter.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided electricaljoint apparatus of high current carrying capacity having particular butnot limited application in switchboard drawout apparatus. The jointapparatus of the invention provides the unique capability of manuallyperfecting from a safe, removed location cool running electrical jointssimilar to and having the attributes of bolted joints. Moreover, theapparatus is effective in perfecting a plurality of such electricaljoints simultaneously in a simple, rapid and reliable manner. Inaddition, a signal feature of the present invention resides in itscapability of generating predetermined and uniformly repeatable jointclamping forces, thus achieving highly reliable electrical joints eachtime they are made. Also of prime significance and advantage is the factthat the joint apparatus of the invention generates equal and oppositelydirected clamping forces on the individual joints and consequently thereis no resultant force acting on the joint apparatus once the joints havebeen perfected.

More specifically, the joint apparatus of the present invention includesan array of spaced first electrical connectors, each equipped withplural contact elements arranged in parallel spaced relation. Alsoincluded in an array of second electrical connectors, each associatedwith a different one of the first connectors and having at least onecontact element arranged for juxtaposition in lapped relation with thecontact elements of its associated first connector. An elongatedclamping rod extends freely through aligned apertures in the contactelements of each of the first electrical connectors and has affixed toone of its ends a first cam follower. A second cam follower is movablymounted on the rod adjacent its one end in juxtaposed relation with thefirst cam follower. First compression spring means is interposed betweenthe second cam follower and the first connector at one end of the array,while second compression spring means is interposed between the firstconnector at the other end of the array and a stop affixed to the otherend of the rod.

Camming means is provided for driven movement between joint clamping andjoint unclamping positions. The camming means while in its unclampingposition engages the first and second cam followers such as to sustainthe first and second compression spring means in substantially unloadedconditions and thus permit the contact elements of associated first andsecond connectors to readily move into and away from lapped relation.However, when the camming means is driven to its clamping position, thefirst and second cam followers are cammed in opposite directions touniformly load the first and second compression spring means and therebydevelop substantially equal and oppositely directed forces effective toclamp the lapped contact elements in secure electrical interconnection.

The electrical joint apparatus of the invention further includesinsulators supported on the rod and filling the spaces between adjacentfirst connectors, such as to achieve electrical isolation therebetweenand also to serve as joint clamping force transmitting elements.Additional insulators electrically isolate the connectors from the rodand the cam followers, and thus the camming means can be manuallypropelled between its clamping and unclamping positions directly orremotely via a drive train in complete safety.

The disclosed embodiment of the present invention specifically directedto implementation in switchboard drawout apparatus includes separatearrays of first connectors and separate arrays of second connectors.Each first connector array is equipped with a clamping rod, compressionspring means and cam followers, all as generally described above. Thecamming means is in the form of separate, rigidly interconnected doubleacting cams positioned to engage the cam followers of each firstconnector array during conjunctive movement between the clamping andunclamping positions. Thus, a common manual drive is effective to propelthe separate cams in unison to their joint clamping positions pursuantto simultaneously generating equal and oppositely directed clampingforces in each first connector array and the plural joints in each ofthe associated first and second connector arrays are achievedconcurrently in an efficient and reliable manner.

The invention accordingly comprises the features of construction andarrangement of parts which will be exemplified in the constructionhereinafter set forth, and the scope of the invention will be indicatedin the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description, taken inconnection with the accompanying drawings, in which:

FIG. 1 is a front perspective view of a switchboard compartment equippedwith circuit breaker drawout apparatus embodying the present invention;

FIG. 2 is a rear perspective view of the drawout apparatus of FIG. 1;

FIGS. 3 and 4 are side elevational views of a circuit breaker carriageutilized in the drawout apparatus of FIG. 1, these figures portrayingthe operation of a racking mechanism included in the drawout apparatus;

FIG. 5 is a fragmentary perspective view of a portion of the drawoutapparatus of FIG. 1 mounted by the switchboard;

FIG. 6 is a fragmentary, somewhat diagramatic, side elevational view ofa portion of FIG. 5, illustrating the action of a gate in controllingthe racking movement of the circuit breaker-carriage assembly betweenits test and disengaged position;

FIG. 7 is a fragmentary, perspective view of a portion of a jointclamping mechanism incorporated in the drawout apparatus of FIG. 1;

FIG. 8 is an isometric view of the back wall of the switchboard cubicalaccommodating the drawout apparatus of FIG. 1;

FIG. 9 is an exploded, perspective view of a portion of the jointclamping mechanism of FIG. 7;

FIG. 10 is a fragmentary, perspective view of a portion of the jointclamping mechanism of FIG. 7 depicted in its joint clamping condition;

FIG. 11 is a fragmentary, plan view, partially broken away, of a portionof the joint clamping mechanism of FIG. 7;

FIG. 12 is a plan view, partially broken away, of a portion of the jointclamping mechanism of FIG. 7, depicted in its joint clamping condition;

FIG. 13 is an exploded, perspective view of a portion of an accesscontrol assembly incorporated in the drawout apparatus of FIG. 1;

FIG. 14 is a perspective view of a portion of the access controlassembly of FIG. 13, illustrating different relative positions of thevarious parts;

FIG. 15 is a fragmentary, perspective view of the access controlassembly of FIG. 13, illustrating the relative positions of the variousparts assumed when the circuit breaker-carriage assembly arrives at itsengaged position;

FIGS. 16 through 19 are a series of perspective views of the accesscontrol assembly in its various conditions to control access to theracking and joint clamping mechanisms;

FIGS. 20 through 23 are a series of side elevational views illustratingthe operation of a position indicator assembly utilized in the drawoutapparatus of FIG. 1;

FIG. 24 is a front elevational view of the position indicator apparatusof FIGS. 20 through 23;

FIG. 25 is a plan view of a position indicia bearing label displayed bythe position indicator apparatus of FIGS. 20 through 23;

FIGS. 26 and 27 are plan views, partially broken away, of a portion ofthe drawout apparatus of FIG. 1 illustrating the manner in which a tripinterlock assembly and the position indicator assembly of FIGS. 20through 23 are controlled by the joint clamping mechanism of FIG. 7;

FIGS. 28 and 29 are sectional views of the trip interlock assembly ofFIGS. 26 and 27, illustrating the manner in which the trip interlockassembly is controlled by the racking mechanism of FIGS. 3 and 4; and

FIG. 30 is an exploded, fragmentary perspective view of a portion of thetrip interlock assembly of FIGS. 26 and 27.

Corresponding reference numerals refer to like parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION

Referring first to FIG. 1, the invention is embodied in a drawoutapparatus for facilitating racking movement of a large, industrial-typecircuit breaker 20 into and out of a cubical or compartment of anelectrical enclosure or switchboard 22. The circuit breaker is mountedby a carriage, generally indicated at 24, which in turn is supported forracking movement by opposed telescoping rail assemblies, generallyindicated at 26 and mounted to the compartment sidewalls 22a. The railassemblies are preferably constructed in the manner disclosed in thecommonly assigned, co-pending application Ser. No. 565,618, filed Apr.14, 1975; the disclosure of this co-pending application beingspecifically incorporated herein by reference. These rail assembliesaccommodate racking movement of circuit breaker 20 between a withdrawnor extended position and a retracted or "engaged" position, wherein thebreaker-switchboard load current carrying primary contact terminals arein engageable relation, ready to be made into cool running joints by aclamping mechanism generally indicated at 27. As disclosed in theabove-noted co-pending application, the rail assemblies accommodatepositioning of the circuit breaker in an intermediate position, commonlyreferred to as the "test" position, wherein the primary contactterminals are disengaged, while circuit breaker-switchboard secondarycontacts remain engaged to permit operational testing of variousassessorial or auxiliary functions embodied in the circuit breaker.Intermediate the extended and test positions is a so-called "disengaged"position wherein both the primary and secondary contacts are disengaged.These engaged, test and disengaged positions of the circuit breaker aredisplayed frontally to the operator of the drawout apparatus by anindicator assembly, generally indicated herein at 30 in FIG. 1. Rackingmovement of the circuit breaker between its extended and test positionsis readily effected manually through the convenience of the railassemblies 26. However, in order to achieve precise positioning of thecircuit breaker in its engaged and test positions, racking movementtherebetween is effected by operation of a racking mechanism, generallyindicated at 32 in FIG. 1.

Carriage 24, as seen in FIGS. 1 and 2, includes a pair of spacedsideplates 34 interconnected across the back by a series of horizontalstringers 36. Bolts 37 clamp laterally extending flanges 20a, integralwith the circuit breaker base, to the carriage stringers 36 pursuant toaffixing the circuit breaker to the carriage. As best seen in FIG. 3, ahorizontally elongated bracket 38 is affixed to each sideplate 34 forthe purpose of mounting front and rear carriage support pins 39. Asdisclosed in the above-noted co-pending application, these pins arereceived in slots provided in the inner rails of each rail assembly inmounting the circuit breaker-carriage assembly thereon. As seen in FIGS.3 and 4 herein, a mounting plate 40, affixed to the right carriagesideplate 34, is formed with a turned out frontal flange 40a whichserves to rotatably mount a lead screw 42 included in racking mechanism32. A collar 43, fitted on lead screw 42 behind flange 40a, cooperateswith the lead screw head to preclude axial movement of the lead screw. Aslideplate 44 is provided with a longitudinally elongated slot 44a whichreceives a laterally outstanding pin 46 carried by mounting plate 40. Abracket 47 is affixed to slideplate 44 and captures a travelling nut 48through which lead screw 42 is threaded. It is seen that slideplate 44is thusly mounted to reciprocate horizontally as the lead screw isrotated in opposite directions via a suitable tool, such as aconventional socket wrench.

Racking mechanism 32 further includes a crank shaft 50 (FIG. 2)extending across the back of the circuit breaker and journaled adjacentits ends in carriage sideplates 34. To the ends of the crank shaft areaffixed right and left crank arm 52. The right crank arm as seen inFIGS. 3 and 4, carries an inwardly extending pin 54 which is received ina vertically elongated slot 44b in slideplate 44. It is thus seen thatreciprocation of slideplate 44 by rotation of lead screw 42 swings theright crank arm 52 through an arc centered about the crank shaft axisvia the pin 54 and slot 44b interconnection. Thus, rotation of the leadscrew 42 in a direction to move the slide to the left from its positionin FIG. 3 to its position in FIG. 4 swings the right crank arm 52 in theclockwise direction. Crank shaft 50 is thus also rotated in theclockwise direction, and the left crank arm affixed to its other end isswung through a corresponding arc. The crank arms mount outwardlyextending crank pins 56 which, as described in detail in the above-notedco-pending application, operate on stationary cam surfaces to achieveracking movement of the circuit breaker-carriage assembly between thetest and engaged positions via operation of racking mechanism 32.

Each rail assembly, as seen in FIG. 5, includes two sets of verticallyopposed rollers 62 which are mounted to the compartment sidewall 22a.These rollers serve to movably mount an intermediate rail 64 which, inturn, mounts a series of rollers 66. These rollers, in turn, movablymount an inner rail 70. It is thus seen that the intermediate rail rideson stationary rollers 62, while the inner rail 70 rides on rollers 66carried by the intermediate rail, thus accommodating telescopic movementof the two rails of each rail assembly in and out. To mount carriage 24to the rail assemblies, each inner rail 70 is provided with front andrear upwardly opening notches 72 which receive the carriage support pins39 (FIG. 3).

As disclosed in the above-noted co-pending application Ser. No. 567,618,the rail assemblies 26 include provisions for limiting the telescopicmovements of the intermediate and inner rails, locking the carriage inits supported position on the rail assemblies, and latching means forlatching the rail assemblies in their extended and compacted conditionsin the absence of the circuit breaker carriage. Also, the railassemblies are structured such that the circuit breaker-carriageassembly may be swung over on the two forward carriage support pins 39to an inverted orientation, thereby facilitating inspection andmaintenance of the circuit breaker and switchboard primary contactterminals.

That portion of the racking mechanism 32 carried by carriage 24, namelythe racking screw 42, slideplate 44, crank arms 52, crank pins 56 etc.have already been described in connection with FIGS. 3 and 4. Theremaining, stationary portion of the racking mechanism is supported byeach compartment sidewall 22a. Thus, as seen in FIG. 5 and as describedin detail in the above-noted co-pending application, a plate 90, affixedto each compartment sidewall, is provided with a double-acting cam slot92 extending from an upwardly directed mouth downwardly and somewhatrearwardly. Crank pins 56 (FIGS. 3 and 4) operate in these cam slots asillustrated in FIG. 6; acting on the forward edges thereof to draw thecircuit breaker-carriage assembly from the test position inwardly to theengaged position and acting on the rearward edges thereof to draw theassembly back to the test position. This action is implemented byrotation of the racking mechanism lead screw 42 in one direction toswing the crank pins downwardly in slots 92 and draw the circuit breakerinto the engaged position and by rotation in the opposite direction toswing the crank pins upwardly in the slots to back the circuit breakeroff to the test position.

Entry and exit of the crank pins 56 from their associated cam slots 92are controlled by pivotally mounted gates 94. Positioning of each gate94 is manually controlled by a separate, elongated gate operator arm 98extending out to the front side edge of the switchboard compartment. Asdescribed more clearly in the above-noted co-pending application, arms98 are pulled out in order to pivot the gates 94 to their open positionseen in FIG. 5 and in phantom in FIG. 6. Latches 100 are provided tohold the operator arms in their pulled out positions against the bias ofreturn springs 101, such as to sustain the gates in their open positionsand thus accommodate movement of the crank pins 56 into the mouths ofcam slots 82 as the circuit breaker-carriage assembly is manually pushedin from the disengaged position to the test position. Latches 100 alsosustain the gates in their open positions to accommodate exiting of thecrank pins 56 as the circuit breaker-carriage assembly is manuallypulled away from the test position into the disengaged position. Thelatches 100 are also equipped to automatically release the arms 98 forretraction by springs 101 to close the gates 94 once the crank pins 56have either entered or left the mouth of cam slots 92. To this end, thelatches 100 are provided with rearward extensions 112. When the latchesare positioned to latch the arms 98 in their pulled out positions, theextensions are elevated into positions where they are engaged by a gateactuating pin 58 (FIGS. 3 and 4) carried by each crank arm 52 as thecircuit breaker-carriage assembly makes its final approach into the testposition and as the assembly exits the test position enroute to thedisengaged position. This engagement unlatches the latches to releasethe arms, and the gates close, all as more clearly described in theabove-noted co-pending application Ser. No. 565,618.

To prevent undesirable rocking and skewing of the circuitbreaker-carriage assembly during its racking movement, a longitudinallyelongated guide channel, generally indicated at 114 in FIGS. 3 and 4, isaffixed to each carriage sideplate 34. Each guide channel consists ofvertically spaced, laterally extending flanges 116a and 116b. Thechannel 118 defined by these flanges is bottomed by a series of spacedposts 120. As seen in FIG. 5, a longitudinally elongated guide flange122 is mounted to each compartment sidewall 22a. Guide flange 122 ismade up of two flange halves between which are captured a series ofrollers 124. During racking movement of the circuit breaker-carriageassembly, guide flange 122 is received in the guide channel 118 withrollers 124 rolling against the upper and lower channel defining flanges116a, 116b to prevent rocking motion of the circuit breaker-carriageassembly during racking movement without adding noticably to therequired racking force. Posts 120 situated in the bottoms of the guidechannels 118 engage the free edges of guide flanges 122 so as to inhibitappreciable skewing motion of the circuit breaker-carriage assemblyduring racking movement.

Returning to FIGS. 1 and 2, circuit breaker 20 is provided with massiveline terminal straps 130 extending upwardly from the breaker case and aplurality of downwardly extending load terminal straps 132. To each lineterminal strap there is clamped in electrical connection, by means ofbolts 131, a separate stab connector 134 (FIG. 2). Similarly, bolts 131secure individual stab connectors 134 to each of the load straps 132. Aswill be seen, the line stab connectors are ganged together to provide aline connector stack assembly 135, while the load stab connectors areganged together to provide a load connector stack assembly 137; bothassemblies being included in the joint clamping mechanism 27. As bestseen in FIG. 7, each stab connector 134 comprises a base 134a which isprovided with tapped bores into which the bolts 131 are threadedpursuant to clamping the connector in electrical connection with itsassociated terminal strap. Integrally formed with connector base 134aare a plurality of parallel spaced contact fingers 134b. As seen in FIG.8, the switchboard 22 is equipped with line and load receiver connectors136 respectively electrically connected to line and load bus (notshown). These switchboard line and load receiver connectors aresimilarly provided with a series of parallel spaced contact fingers136a. Returning to FIG. 7, when the circuit breaker-carriage assembly isin the engaged position, the contact fingers of the associated circuitbreaker stab connectors and switchboard receiver connectors interleave.The spacings between the contact fingers of the associated stab andreceiver connectors are such that they slide freely relative to eachother in assuming their interleaved relationships. Preferably, the lineand load stab connectors are individually secured to elongatedinsulative bars 139 affixed to the carriage stringers 36 as best seen inFIG. 2, and thus the line and load connector stack assemblies may besupported as completed assemblies by the carriage 34, independently ofthe circuit breaker terminal straps.

Referring jointly to FIGS. 7 and 9 through 12, the contact fingers 134bof each of the identically constructed line and load connector stackassemblies 135, 137 are provided with transversely registered apertures134c through which extends an elongated clamping rod 140 (FIG. 11). Aninsulating sleeve 142 encompasses the clamping rod 140 so as toelectrically insulate the rod from the individual contact fingers.Centrally apertured insulator blocks 144 are loosely fitted on clampingrod 140 to take up the space between adjacent stab connectors 134.Similar, centrally apertured insulator blocks 144 are loosely receivedon each end portion of clamping rod 140 beyond the outboard stabconnectors 134. The left end of clamping rod 140 passes through acentral opening in a U-shaped clamping plate 146 and terminates in athreaded portion accommodating a nut 148. Captured on the left end ofclamping shaft 140 intermediate nut 148 and clamping plate 146 are aseries of four Belleville washers 150. A sheet 151 of insulation isinterposed between clamping plate 146 and the left most insulator block144 so as to increase the over surface clearance between the outboardconnector and the metal part therebeyond.

The right end of clamping rod 140 of each connector stack assemblypasses through another U-shaped clamping plate 146, an insulative sheet151, and a series of four Belleville washers, terminating in a tongue152 having formed therein a rectangular opening 152a, as best seen inFIG. 9. A U-shaped clamping element 154 is formed having an aperture154a in its bight portion 154b through which the right end clamping rod140 freely passes. The legs 154c of clamping element 154 are spacedapart sufficiently to receive therebetween tongue 152 at the right endof clamping rod 140. Rectangular openings 154d are provided in theclamping element legs 154c in opposed relation with rectangular opening152a in tongue 152.

As best seen in FIG. 2, a vertically oriented clamping shaft 160, alsoincluded in the joint clamping mechanism 27, is journaled for axialrotation by brackets 162 affixed to the upper and lower carriagestringers 36. The upper and lower terminal portions of this clampingshaft are provided with opposed flats 160a (FIG. 9), with these terminalportions extending through the rectangular openings in the clampingelement 154 and tongue 152 of both line and load connector stackassemblies 135, 137. In the quiescent condition of joint clampingmechanism 27, clamping shaft 160 is angularly oriented as seen in FIG.7, such that the flats 160a at its terminal end portions are arrangedperpendicular to the axis of clamping rod 140. Thus, these flats engagethe outer edges of the rectangular openings 152a in tongues 152 and theinner edges of rectangular openings 154d in clamping elements 154.

Still considering the joint clamping mechanism 27, a bracket 170 isattached to the inner side of the right carriage sideplate 34, as seenin FIG. 11. The forward portion of this bracket is laterally turned toprovide a flange 170a for rotably mounting a lead screw 172. A collar174 fitted to lead screw 172 behind flange 170a prevents axial movementof the lead screw. A sideplate 176 is mounted for reciprocating movementby a bracket mounted pin 177 received in a longitudinally elongated slot176a visible in FIG. 16. The slideplate captures a traveling nut 178through which lead screw 172 is threaded. A transversely elongated slot176b formed in slideplate 176 receives a pin 180 carried at the free endof a crank arm 182 affixed at its other end of clamping shaft 160, asbest seen in FIG. 9. It is thus seen that rotation of clamping screw 172via a suitable tool, such as a socket wrench, reciprocates slide 176,which in turn, via crank arm 182, rotates clamping shaft 160.

With the contact fingers of the switchboard receiver connectors and theline and load connector stack assemblies interleaved, rotation of theclamping shaft 160 swings the rounded portions of its shaft terminationsinto engagement with the opposed edges of the rectangular openings inthe tongues 152 and clamping elements 154 of both stack assemblies. As aresult, tongues 152 are cammed to the right as seen in FIG. 10, pullingwith it clamping rod 140 and thereby loading the Belleville washers 150at the left ends of both the line and load connector stack assemblies.At the same time, clamping elements 154 are cammed to the left as seenin FIG. 10 to load the Belleville washers 150 at the right ends of theline and load connector stack assemblies. These Belleville washers ateach end of the joint stack assembly develop oppositely directedclamping forces effective to clamp the interleaved contact fingers ofthe circuit breaker stab and switchboard receiver connectors in secureelectrical connection.

While the joint clamping mechanism together with its line and loadconnector stack assemblies are disclosed as being mounted by thecarriage, it will be appreciated that this mechanism could be mountedinstead by the switchboard. Preferably, the stab connectors 134 are eachprovided with one more contact finger 134b than is provided in each ofthe receiver connectors 136, as illustrated herein, and consequently thestab contact fingers can effectively define all of the slots into whichthe receiver contact fingers 136a are inserted.

It will be appreciated that the disclosed joint clamping mechanismoffers numerous advantages. The designed differential in the effectivediameters of the clamping shaft flats 160a versus the rounded portionsof the shaft terminations is operative to impart a predetermined andvery repeatable loading or compression of the sets of Belleville washersat each end of both stack assemblies. Thus, the clamping forcesdeveloped by the opposed sets of spring washers are equallypredetermined and repeatable. Since these clamping forces areessentially equal and oppositely directed, there is no significantresultant forces acting on the connector stack assemblies. Jointclamping forces of as much as 3,000 pounds have been achieved utilizingthe disclosed joint clamping mechanism. The nuts 148, threaded on theends of the clamping rods 140, are turned to readily establish thedesired clamp force magnitude. While Belleville washers are illustratedherein, it will be understood that other forms of joint clamping forcegenerating springs may be utilized. Also to be noted is the fact thatthe disclosed joint clamping mechanism affords the opportunity toperfect high current carrying primary terminal joints from the front ofthe switchboard in complete safety even while the switchboard linereceiver connectors are live. Moreover, all phases of both the line andload primary terminal joints are perfected concurrently in convenientfashion, with the joints having all the attributes of bolted joints.While the joint clamping mechanism is herein disclosed in itsapplication to effecting electrical joints between a switchboard and anelectrical device, it will be appreciated that the teachings may bereadily applied to the making of high current carrying electrical jointsin general, such as between busway sections and between busway andbusway plugs.

As a safety measure, it is deemed appropriate to interlock theoperations of the racking mechanism 32 and the joint clamping mechanism27, depending upon the position of the circuit breaker-carriageassembly. That is, it is very important that the clamping screw 172 notbe rotated to exert clamping pressures on the line and load connectorstack assemblies until the circuit breaker is in its engaged positionwith the contact fingers of the stab and receiver connectors fullyinterleaved. It will be appreciated that permanent deformation of thecircuit breaker stab connector fingers could well result if clampingpressure is exerted absent the interleaved switchboard receiver contactfingers. Also, interleaving of the contact fingers could not be achievedas the circuit breaker is racked into its engaged position if theconnector stack assemblies were pre-clamped, and attempts to do so woulddamage the racking mechanism 32. By the same token, attempts to rack thecircuit breaker-carriage assembly away from its engaged position withoutfirst unclamping the joint stack assemblies could also damage theracking mechanism.

To this end, an access control assembly, generally indicated at 179 inFIGS. 1 and 16 through 19, is provided to include a first access controlplate 180 having vertically elongated slots 180a through which arereceived pins 181 pursuant to vertically reciprocatively mounting theplate to the inner side of the right carriage sideplate 34 as best seenin FIGS. 13 through 15. This access control plate further includes anoffset and upwardly extending barrier 180b which, with the plate in itselevated position, partially overlies the head clamping screw 172, thusdenying access thereto. Riveted to access control plate 180 is afaceplate 182, which is provided with a lower offset tab 182ato serve asa handle for manually vertically positioning the access control assembly179. A second access control plate 184 is mounted by a pivot pin 185between the first access control plate 180 and faceplate 182. The secondaccess control plate 184 is provided with an offset and dependingbarrier 184a which is adapted to control access to the head of rackingscrew 42, depending upon the vertical position of the access controlassembly and the angular position of the second access control plate. Aspacer rivet 186 extending between faceplate 182 and access controlplate 180 through an elongated slot 184b in the second access controlplate 184 (FIG. 17) holds these plates is spaced relation to accommodateplate 184. A clamping screw 187 is adjusted to squeeze the two outerplates together so as to exert a light frictional drag on the pivotalmovement of the second access control plate and thus discourage spuriouspivotal movement of access control plate 184 during verticalreciprocation of the access control assembly 179.

From the description thus far, it is seen that while the second accesscontrol plate 184 is in its counterclockwise most pivotal position seenin FIG. 16, its barrier 184a is in position to deny access to theracking or drawout screw 42 while the access control assembly 179 is inits depressed position. However, barrier 180b is the ducked away fromthe head of clamping screw 172 such as to afford access thereto. Whenthe access control assembly is in its elevated position seen in FIG. 19,barrier 180b is in position to deny access to clamping screw 172, whilebarrier element 184a is elevated away from the head of racking screw 42to admit access thereto. With the access control assembly in itselevated position and the control plate 184 pivoted to itsclockwise-most position as illustrated in FIG. 17, access to bothracking screw 42 and clamping screw 172 is denied. In this condition,aperture 182b in faceplate 182, aperture 184d in control plate 184, andaperture 180c in control plate 180 (FIG. 13) are in registry to receivethe hasp of a padlock 188.

To interlockingly regulate the movement of the access control assemblyaccording to the circuit breaker-carriage assembly position, a slide 190is mounted to the underside of the lower guide channel flange 116b(FIGS. 3, 4 and 13 through 15) for limited fore and aft movement. Aspring 192, operating between a turned down tab 190a at the rear end ofslide 190 and a post 193 depending from guide channel flange 116b,biases the slide to its rearward position. An arm 194 adjustably mountedto the underside of guide flange 122 (FIGS. 5 and 13), carries alaterally extending tab 194a which is positioned to engage a turned downtab 190a, shifting slide 190 to its forward position as the circuitbreaker-carriage assembly is racked to its engaged position. The forwardend of arm 194 is turned up to provide a convenient handle for adjustingthe mounting position of the arm such that slide 190 is shiftedsufficiently forward upon arrival of the circuit breaker-carriageassembly in its engaged position to register a notch 190b formed thereinwith a laterally turned tab 180d carried by access control plate 180. Atab 190c depending from slide 190 just forward of notch 190b, preventsaccess control plate tab 180d from getting caught under the slide. Oncethe appropriate position of arm 194 is established, it is immovablyclamped to the underside of guide flange 122. It is seen from FIG. 13,that until slideplate 190 is shifted to its forward position byengagement with arm tab 194a upon arrival of the circuit breaker in itsengaged position, notch 190b is out of registry with tab 180d, andaccess control assembly 179 cannot, under this circumstance, be shifteddownwardly to afford access to clamping screw 172.

As an additional precautionary measure, a flange 196 is riveted to theracking screw slideplate 44, as seen in FIGS. 3, 4, 14 and 15. The upperelongated edge 196a of this flange is positioned in underlying relationto access control plate tab 180d, as to prevent downward movement of theaccess control assembly until the racking mechanism has been operated todraw the circuit breaker-carriage assembly into the engaged position.Once in the engaged position, flange 196 has moved completely forward ofthe access control plate tab 180d, as seen in FIGS. 4 and 15, thusclearing tab 180d to move downwardly through notch 190b and beyond theback edge of flange 196. These two separate, but functionally relatedinterlocking provisions are seen to prevent inadvertant, untowardoperation of the joint clamping mechanism, both while the circuitbreaker-carriage assembly is mounted or dismounted with respect to therail assemblies 26.

With the circuit breaker-carriage assembly in its engaged position andthe access control assembly freed to be shifted downwardly to access theclamping screw while, at the same time, denying access to the rackingscrew, clamping operation of the connector stack assemblies then mayproceed. As the clamping mechanism slideplate 176 is drawn forwardly byrotation of clamping screw 172, it moves over an upstanding tab 180ecarried by access control plate 180 (FIGS. 15 and 16) so as to preventelevation of the access control assembly during the time that clampingpressures are being exerted on the connector stack assemblies, andconsequently, access to the racking screw 42 is, under thiscircumstance, denied.

It is preferred that the access control assembly can only be locked bypadlock 188 when the circuit breaker-carriage assembly is in either itstest or engaged positions. To this end, the pivotal access control plate184 is provided with a laterally extending tab 184c which is received inone of two sets of notches 200a and 200b formed in the upper edges ofboth the right gate control arm 98 and a bracket 202 supporting same, asseen in FIGS. 5, 16 and 17. These notches are positioned such that theset 200a is aligned with tab 184c when the circuit breaker-carriageassembly is in its test position and the set 200b is aligned with thetab when the assembly is in its disengaged position. For the engagedposition of the assembly, tab 184c is not registerable with either ofthese notch sets, and consequently access control plate 184 cannot bepivoted sufficiently clockwise to align its hasp aperture 184d with thehasp apertures in the faceplate and access control plate 180 such as topermit padlocking. However, with tab 184c lodged in either of thenotches sets 200a, 200b and the padlock applied, racking movement of thecircuit breaker-carriage assembly and operation of the gate control armare both precluded, and the access control assembly is locked in thecondition denying access to both lead screws 42 and 172.

The present drawout apparatus includes position indicating apparatussimilar to that disclosed and claimed in the commonly assigned,co-pending application Ser. No. 567,619, filed Apr. 14, 1975. In thedrawout apparatus of this co-pending application, there were only threesignificant circuit breaker-carriage positions, namely, the disengaged,test and engaged positions. In the instant drawout apparatus, there isan additional position, which is in actuality a condition, namely, thejoint clamped position. In terms of circuit breaker-carriage assemblyposition, the engaged and clamped positions are the same. The clampedposition pertains when the circuit breaker stack connector assembliesare clamped in electrical connection with the switchboard receiverconnectors. Accordingly, the position indicating apparatus 30 of thepresent drawout apparatus is structured so as to indicate not only thedisengaged, test and engaged positions of the circuit breaker-carriageassembly, but also the clamped condition of the circuitbreaker-switchboard primary contact terminals.

To this end, the position indicator assembly 30 includes, as seen inFIGS. 20 through 23, an arm 210 pivotally mounted at 212 to a bracket213 affixed to the left carriage sideplate 34. The forward portion ofarm 210 is laterally offset away from bracket 213 and terminates in abent flag 214 to which is affixed label 214a (FIG. 25) bearing the words"Disengaged", "Test", "Engaged" and "Clamped", one below the other. Alaterally turned front end portion 213a of bracket 213 is provided witha rectangular opening 213b (FIG. 24) behind which is affixed a mask 215having a window 215a in which the label indicia is separately displayed.A flange 216 turned back from the side edge of flag 214 opposite itsjunction with arm 210 carries an upper stop 216a and a lower stop 216bwhich engage a stop pin 217 carried by bracket 213 to determined thelimits of pivotal movement of indicator arm 210, as best seen in FIG.20. The arm is biased downwardly in the clockwise direction by a spring220 anchored to a post 221 carried by bracket 213.

As disclosed in the above-noted co-pending application, Ser. No.567,619, the bottom edge of indicator arm 210 is machined to provide astep cam having a series of straight cam segments 210a, 210b, and 210cand 210d interconnected by sharply angled cam segments 210e. Operatingagainst this step cam is a stationary indicator actuator 222 fixedlymounted by the compartment sidewall. It is thus seen that as the circuitbreaker-carriage assembly is moved in and out, the indicator arm 120 isvariously angularly positioned depending upon which step cam segment isriding on actuator 222. By correlating the positioning of the indicia onthe label 214a affixed to flag 214 with these cam segments, the positionof the circuit breaker-carriage assembly can be read through the window215a in mask 215. Thus, when cam segment 210a is riding on actuator 222(FIG. 23), the word "disengaged" is visible in window 215a. As thecircuit breaker-carriage assembly is pushed into the test position, camsegment 210b rides onto actuator 222 and arm 210 is pivoted upwardly toindex the word "test" into registry with window 215a. By virtue of thesharply angled transistion cam segment 210e the change in positionindication is rather abrupt, occurring essentially upon arrival of thecircuit breaker-carriage assembly at its test position. From the testposition, the circuit breaker-carriage assembly is drawn toward theengaged position by the racking mechanism 32. Cam segment 210c thenrides onto actuator 222, and the indicator arm 210 is pivoted upwardlyto register the blank space between the words "test" and "engage" inwindow 215a. This blank indication advises the operator that the circuitbreaker-carriage assembly is in neither the test position nor theengaged position, but is in transient therebetween. Upon arrival at theengaged position, cam segment 210d rides onto actuator 222, pivoting arm210 upwardly still another increment to register the word "engaged" inwindow 215a. Though in the engaged position, the circuit breaker mustnot be turned on until the switchboard-circuit breaker primary contactterminals are clamped in electrical interconnection by operation ofjoint clamping mechanism 27.

In order to indicate achievement of the clamped condition, the fact ofcompleted operation of the clamping joint clamping mechanism must becommunicated to the indicator assembly. To this end, a slide 230,elongated to extend substantially the full width of the carriage 24, ismounted by one of the rear carriage stringers 36, as seen in FIG. 2.More specifically, and as best seen in FIGS. 26 and 27, slide 230 isformed having a series of longitudinally elongated slots 230a in whichare received pins 232 carried by the slide supporting stringer 36. Thismounting affords limited longitudinal movement of the slide against theforce of a spring 236 normally biasing the slide to its right-mostposition seen in FIG. 27. The left end of this slide seen in FIGS. 26and 27 mounts a bracket 234 carrying an arm 234a. An adjusting screw 235threaded through a laterally turned flange portion 234b of bracket 234bears against arm 234a to adjust its positioning so as to bear againstthe periphery of clamping shaft 160 when the slide is in its right-mostposition. Clamping shaft 160 is provided with a bolt 238 extendingdiametrically through the clamping shaft at an elevation aligned witharm 234a of bracket 234. Upon operation of the joint clamping mechanismto perfect the circuit breaker-switchboard primary contact terminals,clamping shaft 160 is rotated, bringing the head of the bolt around intoengagement with arm 234a, as seen in FIG. 26, thereby shifting slide 230to its left-most position at the conclusion of the joint clampingoperation.

An arm 240 is pivotally mounted at 240a to the slide mounting stringer36 adjacent the right end of the slide 230 seen in FIGS. 26 and 27 andis provided at one end with an elongated slot 240b in which is receiveda pin 242 carried by the slide. It is thus seen that the lateralshifting of the slide position produces pivotal movement of arm 240. Theother end of arm 240 from post 242 carries a laterally extending tab240c which extends through an opening 243 in the adjacent carriagesideplate 34. A wire link 244 is hooked at one end to tab 240c of arm240 and extends through an aperture in a bracket 246 carried byindicator arm 210, as seen in FIGS. 20 through 23. The free end of link244 is threaded to receive nuts 248 which are adjustably positioned toestablish the appropriate length of link 244. In comparing FIGS. 20 and21, it is seen that with the circuit breaker-carriage assembly in theengaged position and its primary contact terminal joints with theswitchboard still to be clamped, cam surface 210d is riding on actuator222. Upon actuation of the clamping mechanism to its completed jointclamping condition, the bolt head 238 carried by shaft 160 shifts slide230 to the left as seen in FIG. 26, pivoting arm 240 in a direction todraw the link 244 to the left as seen in FIG. 20, thereby liftingindicator arm 210 upwardly off of actuator 222 sufficiently to registerthe word "clamped" in window 215a. As the joint clamping mechanism isoperated to relax the joint clamping pressure, clamping shaft 160rotates to swing the head of bolt 238 away from arm 234a, and slide 230is returned to the right by its spring 236. Arm 240 is thus pivoted inthe opposite direction to shift link 244 to the right as seen in FIG.21, permitting arm 210 to drop back down onto actuator 222 under thebias of spring 220, thereby again registering the term "engaged" inwindow 215a.

In addition to the safety interlocking features provided by the accesscontrol assembly 179 operating to control access to the joint clampingmechanism 27 and the racking mechanism 32 depending upon the position ofthe circuit breaker-carriage assembly, the instant drawout apparatusalso includes circuit breaker trip interlocking provisions similar tothat disclosed and claimed in the commonly assigned, co-pendingapplication, Ser. No. 567,616, filed Apr. 14, 1975. In this co-pendingapplication, the trip interlock functioned to automatically enableclosure of the circuit breaker while in either its test or engagedpositions and to automatically trip the circuit breaker, should it be inits ON condition, during initial racking movement from the test positiontoward the engaged position and from the engaged position toward thetest position. Thus the trip interlock functions to insure that thecircuit breaker contacts are open during racking movement between thetest and engaged positions, so as to preclude the possibility of loadcurrent flowing through the plug-in primary disconnect contacts whilethey are in the process of being engaged and disengaged. In the case ofthe drawout apparatus disclosed in the present application, circuitbreaker trip interlocking, insofar as the test position is concerned, isperformed in the manner described in the above-noted co-pendingapplication. However, to defeat the trip interlock upon arrival of thecircuit breaker-carriage assembly at its engaged position, as was donein the drawout apparatus of the co-pending application, would create ahazardous situation, since inadvertent closure of the circuit breakercontacts before the circuit breaker-switchboard primary contactterminals have been clamped could have disastrous consequences.

Accordingly, as described below, the trip interlock of the instantdrawout apparatus is conditioned by the racking mechanism to permitclosure of the circuit breaker contacts while in the test position andto trip the circuit breaker should its contacts be left closed asracking movement is initiated from the test position toward the engagedposition. Once in the engaged position, the trip interlock is controlledby the joint clamping mechanism such as to prevent closure of thecircuit breaker contacts until the circuit breaker-switchboard primarycontact terminals have been completely clamped in electricalinterconnection and to trip the circuit breaker should its contacts beclosed during initial operation of the joint clamping mechanism towardrelaxing the joint clamping pressure.

A trip interlock, generally indicated at 250 in FIGS. 2, 26 and 27,includes bracket 252 affixed by suitable means (not shown) to the samerear carriage stringer which mounts slide 230. This bracket mounts aplunger 254 which is normally biased rearwardly in FIG. 27 or to theleft in FIG. 28 by a spring 256. The outer end of plunger 254 is neckeddown for engagement with an elongated lever 258 pivotally mounted at 259to bracket 252. The spring 256 is thus effective through plunger 254, tobias the free, right end of lever 258 rearwardly away from circuitbreaker 20, as seen in FIG. 27. The inner end of plunger 254 carries acam follower plate 260 having a crooked end 260a which is urged byspring 256 into engagement with the periphery of crank shaft 50, as bestseen in FIG. 28.

An extension 258a of lever 258 is engaged under the head of a screw 262adjustably threaded into the end of a plunger 264 which is suitablyslideably mounted for protrusion through the circuit breaker case intocontrolling engagement with a circuit breaker tripping element 266. Aspring 268 acting between the lever extension arm 258a and plunger 264accommodates any over travel of the lever 258 in operating the circuitbreaker tripping element 266, as occasioned by manufacturing tolerances.

To operate trip interlock 250 off the racking mechanism 32, a bolt 269,mounted transversely through crank shaft 50, is so positioned that itshead engages the crooked end 260a of cam follower plate 260 therebydepressing plunger 254 when the racking mechanism accommodates thecircuit breaker-carriage assembly to its test position. Depression ofplunger 254 pivots lever 258 toward the circuit breaker forcing plunger264 inwardly, or to the right as seen in FIG. 29, thereby depressing thetripping element 266 to enable closure of the circuit breaker contacts.As the racking mechanism is operated to move the circuitbreaker-carriage assembly away from the test position toward the engagedposition, the head of bolt 269 carried by crank shaft 50 swings awayfrom cam follower plate 260, and spring 256 returns lever 258 andplunger 264 to their positions shown in FIG. 28. Tripping element 266 isthus released and the circuit breaker is automatically tripped andcannot be reset and closed.

The above described construction and operation of trip interlock 250 aresimilar to that disclosed in the above-noted co-pending application.However, instead of mounting a second transverse bolt in the crank shaftto actuate the trip interlock upon arrival of the circuitbreaker-carriage assembly at its engaged position, the instant tripinterlock utilizes a second lever 270 which is operated by slide 230moving in response to operation of the joint clamping mechanism 27.Thus, as seen in FIGS. 26 and 27, lever 270 is pivotally mounted by apin 272 affixed to rear carriage stringer 36 through a longitudinallyelongated slot 273 in slide 230. A spring 274 normally biases lever 270in the counterclockwise direction as seen in FIGS. 26 and 27. A wirelink 276 interconnects the free end of lever 270 and slide 230 totranslate longitudinal movement of the slide into pivotal movement ofthe lever.

The free end of lever 270 carries an actuating tab 278 poised to engageand depress plunger 254 when lever 270 is pivoted in the clockwisedirection by link 276 in response to the slide 230 being shifted to theleft as seen in FIG. 26 by the clamping shaft mounted bolt head 238 uponcompletion of the joint clamping operation. Depression of plunger 254pivots lever 258 inwardly to achieve depression of plunger 264, which,in turn, depresses tripping element 266 to enable operation of thecircuit breaker to its ON condition. As the joint clamping mechanism 27is operated preparatory to relaxing the joint clamping pressure, bolthead 238 releases slide 230, which is returned to the right by itsspring 236. Link 276 thus releases the free end of lever 270, and spring274 pivots this lever around in the counterclockwise direction,releasing plunger 254. Its return spring 256 then acting through lever258, retracts plunger 264, releasing the tripping element 266. Thecircuit breaker is thus automatically tripped, as well as being disabledfrom being reset and turned on until the joint clamp pressure is fullyrelaxed and the circuit breaker-carriage assembly backed out to the testposition.

It will thus be seen that the objects set forth above, among those madeapparent in the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having described the invention, what is claimed as new and desired tosecure by Letters Patent is:
 1. Electrical joint apparatus comprising,in combination:A. an array of spaced first electrical connectors, eachhaving plural contact elements arranged in parallel spaced relation; B.an array of second electrical connectors, each associated with adifferent one of said first connectors and having at least one contactelement arranged for juxtaposition in lapped relation with said contactelements of its associated one of said first connectors; C. an elongatedclamping rod extending freely through apertures in the contact elementsof each said first electrical connector; D. a first cam follower affixedto one end of said rod; E. a second cam follower movably supported onsaid rod adjacent said one end thereof in juxtaposed relation with saidfirst cam follower; F. first compression spring means interposed betweensaid second cam follower and the first connector at one end of saidarray; G. a stop affixed to the other end of said rod; H. secondcompression spring means interposed between said stop and the firstconnector at the other end of said array; and I. camming means movablebetween joint clamping and joint unclamping positions, said cammingmeans while in said unclamping position controllably engaging said firstand second cam followers to sustain said first and second compressionspring means in substantially unloaded conditions to thereby permit saidcontact elements of said first and second connectors to move into andaway from lapped relation, said camming means operable in said clampingposition to cam said first and second followers in opposite directionsto uniformly load said first and second spring means such as to developsubstantially equal and oppositely directed forces effective to clampsaid lapped contact elements in secure electrical interconnection. 2.The electrical joint apparatus defined in claim 1, which furtherincludes insulators supported on said rod, said insulators taking up thespaces between adjacent first connectors.
 3. The electrical jointapparatus defined in claim 2, which further includes additionalinsulators supported on said rod intermediate said first compressionspring means and the first connector at one end of said array andintermediate said second compression spring means and the firstconnector at the other end of said array.
 4. The electrical jointapparatus defined in claim 3, which further includes an insulatingsleeve carried on said rod to electrically isolate said rod from thecontact elements of said first connectors.
 5. The electrical jointapparatus defined in claim 4, wherein said stop is adjustably affixed onsaid rod while said camming means is in said joint clamping position toestablish the magnitude of the clamping forces.
 6. The electrical jointapparatus defined in claim 3, which further includes a pressure platecarried on said rod and interposed between said first and secondcompression spring means and said additional insulators at each end ofsaid first connector array.
 7. The electrical joint apparatus defined inclaim 3, wherein said first and second compression spring meanscomprises Belleville washers carried on said rod.
 8. The electricaljoint apparatus defined in claim 3, wherein said first cam follower isformed having a first rectangular aperture, and said second cam followercomprises a U-shaped member including parallel spaced legs joined by abight having formed therein a clearance hole through which said rodextends to its junction with said first cam follower accommodatedbetween said legs, said legs having formed therein second rectangularapertures disposed on opposite sides said first rectangular aperture,said camming means positioned within said first and second rectangularapertures in camming engagement with the edges thereof.
 9. Theelectrical joint apparatus defined in claim 8, wherein said cammingmeans comprises a double acting cam having opposed arcuate cam surfaceslying on a common circle, said arcuate cam surfaces being separated byopposed flat cam surfaces, said arcuate cam surfaces engaging one edgeof said first rectangular aperture and the oppositely situated edges ofsaid second rectangular apertures with said cam in said joint clampingposition, and said flat cam surfaces engaging said one edge of saidfirst rectangular aperture and said oppositely situated edges of saidsecond rectangular apertures with said cam in said joint unclampingposition.
 10. Electrical joint apparatus comprising, in combination:A.first and second separated arrays of spaced stab electrical connectors,each said stab connector having plural contact elements arranged inparallel spaced relation; B. first and second arrays of spaced receiverelectrical connectors, each said receiver connector of said first arrayassociated with a different one of said stab connectors of said firstarray and each said receiver connector of said second array associatedwith a different one of said stab connectors of said second array, eachsaid receiver connector having at least one contact element arranged forjuxtaposition in lapped relation with said contact elements of itsassociated one of said stab connectors; C. a separate elongated clampingrod extending freely through apertures in the stab connector contactelements of each said first and second stab connector arrays; D. a firstcam follower affixed to one end of each said rod; E. a second camfollower movably supported on each said rod adjacent said one endthereof in juxtaposed relation with each said first cam follower; F.first compression spring means interposed between each said second camfollower and the stab connector at one end of each said first and secondstab connector arrays; G. a stop affixed to the other end of each saidrod; H. second compression spring means interposed between each saidstop and the stab connector at the other end of each said first andsecond arrays; and I. camming means movable between joint clamping andjoint unclamping positions, said camming means while in said unclampingposition controllably engaging said first and second cam followers ofeach said first and second stab connector arrays to sustain said firstand second compression spring means of each said first and second stabconnector arrays in substantially unloaded conditions to thereby permitsaid contact elements of associated stab and receiver connectors toreadily move into and away from lapped relation, said camming meansoperable in said clamping position to cam said first and second camfollowers of each said first and second stab connector arrays inopposite directions to concurrently, uniformly load said first andsecond spring means of each said first and second stab connector arrayssuch as to develop substantially equal and oppositely directed forceseffective to clamp said lapped contact elements of said first and secondstab and receiver connector arrays in secure electrical interconnection.11. The electrical joint apparatus defined in claim 10, wherein saidcamming means comprises a separate cam acting on the cam followers ofeach said first and second stab connector arrays, a shaft supportingsaid cams and spanning the separation between said first and second stabconnector arrays, and means for selectively rotating said shaft toconcurrently move said cams between said clamping and unclampingpositions.
 12. An electrical joint apparatus comprising, incombination:A. at least one first electrical connector having pluralcontact elements arranged in generally parallel spaced relation; B. asecond electrical connector having at least one contact element arrangedfor juxtaposition in lapped relation with at least one of said contactelements of said first connector; C. a clamping rod extending freelythrough apertures in the contact elements of each said first connector;D. a first cam follower affixed to one end of said rod; E. a second camfollower movably supported on said rod adjacent said one end thereof injuxtaposed relation with said first cam follower; F. a stop affixed tothe other end of said rod; G. a first compression spring supported onsaid rod intermediate said second cam follower and said first connector;H. a second compression spring supported on said rod intermediate saidstop and said first connector; and I. a cam mounted for movement betweenjoint clamped and joint unclamped positions, said cam havinginterconnected high and low cam surfaces, with said cam in saidunclamped position, said low cam surface engaging said first and secondcam followers to sustain said first and second springs in substantiallyuncompressed conditions such as to permit said contact elements of saidfirst and second connectors to readily move into and out of lappedrelation, with said cam in said clamped position, said high cam surfacecamming said first and second cam followers in opposite directions toimpart a predetermined equal degree of compression to said first andsecond springs, said compressed springs developing equal and oppositeforces clamping said lapped contact elements in secure electricalinterconnection.
 13. The electrical joint apparatus defined in claim 12,which further includes at least one additional first connector and anadditional second connector each having contact elements arranged forjuxtaposition in lapped relation, an additional clamping rod extendingfreely through apertures in the contact elements of said additionalfirst connector, additional first and second cam followers respectivelyaffixed to one end of said additional clamping rod and movably supportedon said additional clamping rod adjacent said one end thereof injuxtaposed relation with said additional first cam follower, anadditional stop affixed to the other end of said additional clampingrod, additional first and second compression springs respectivelysupported on said additional clamping rod intermediate said additionalsecond cam follower and said additional first connector and intermediatesaid additional stop and said additional first connector, and anadditional cam mounted for movement between joint clamped and jointunclamped positions, said additional cam likewise having interconnectedhigh and low cam surfaces camming said additional first and second camfollowers in opposite directions to selectively control the compressedconditions of said additional first and second compression springs inclamping and unclamping said lapped contact elements of said additionalfirst and second connectors, and means interconnecting said additionalcam and said first mentioned cam for concerted movement between saidjoint clamped and unclamped positions to concurrently clamp and unclampthe lapped contact elements of said first and second connectors and thelapped contact elements of said additional first and second connectors.14. Electrical joint apparatus comprising, in combination:A. first andsecond arrays of spaced first electrical connectors, each said firstconnector having plural contact elements arranged in parallel spacedrelation; B. first and second arrays of spaced second electricalconnectors, each said second connector of said first array associatedwith a different one of said first connectors of said first array andeach said second connector of said second array associated with adifferent one of said first connectors of said second array, each saidsecond connector having at least one contact element arranged forjuxtaposition in lapped relation with said contact elements of itsassociated one of said first connectors; C. a separate elongatedclamping rod extending freely through apertures in the first connectorcontact elements of said first and second arrays; D. insulatorssupported on each said rod to fill the spaces between adjacent firstconnectors of each array; E. separate cam follower means supported on acorresponding one end of each said rod; F. a stop affixed to thecorresponding other end of each said rod; G. compression spring meansinterposed between said stop and cam follower means of each array; andH. camming means movable between joint clamping and joint unclampingpositions, said camming means, while in said unclamping position,controllably engaging both said cam follower means supported on eachsaid rod to sustain both said compression spring means in substantiallyunloaded conditions to thereby permit said contact elements ofassociated first and second connectors to readily move into and awayfrom lapped relation, said camming means operable in said clampingposition to simultaneously cam both said cam follower means in a mannerto uniformly load both said compression spring means, said loadedclamping spring means clamping said lapped contact elements ofassociated first and second connectors of said first and second arraysin secure electrical interconnection.
 15. The electrical joint apparatusdefined in claim 14, wherein said camming means comprises a separate camacting on each of said cam follower means, a shaft supporting said camsand spanning the separation between said first and second arrays offirst and second connectors, and means for selectively rotating saidshaft to concurrently move said cams between said clamping andunclamping positions.